Knowledge Base

Dell PERC controller disk Patrol Read


The Patrol Read feature is designed as a preventative measure to ensure physical disk health and data integrity.



The Patrol Read feature is designed as a preventative measure to ensure physical disk health and data integrity. Patrol Read scans for and resolves potential problems on configured physical disks. The OpenManage storage management application can be used to start Patrol Read and change its behavior.

Patrol Read Behavior

The following is an overview of Patrol Read behavior:

  1. Patrol Read runs on all disks on the controller that are configured as part of a virtual disk, including hot spares.
  2. Patrol Read does not run on physical disks that are not part of a virtual disk or are in Ready state.
  3. Patrol Read adjusts the amount of controller resources dedicated to Patrol Read operations based on outstanding disk I/O. For example, if the system is busy processing I/O operation, then Patrol Read uses fewer resources to allow the I/O to take a higher priority.
  4. Patrol Read does not run on any disks involved in any of the following operations:
    • Rebuild
    • Replace Member
    • Full or Background Initialization
    • Consistency Check
    • RLM or OCE

Patrol Read Modes

Patrol Read Mode can be set in BIOS configuration utility and UEFI RAID Configuration Utility. The default Patrol Read mode is automatic. When Patrol Read is in automatic mode, Patrol Read runs automatically at its scheduled interval.

Below is a summary of the different Patrol Read modes:

  • In Auto Mode, Firmware allows Patrol Read to be started manually
  • In Auto Mode, Patrol Read can be stopped manually.
  • In Manual Mode, Patrol Read does not start automatically as per the scheduled time.
  • In Manual Mode, Patrol Read can be started manually.
  • In Manual Mode, Patrol Read can be stopped manually.
  • In Disabled Mode, Patrol Read will not run automatically.
  • In Disabled Mode, Patrol Read cannot be started manually.
Note: Patrol Read automatically runs every seven days on configured SAS and SATA HDDs. Patrol Read is not necessary on SSD and is disabled by default.

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Article ID: SLN292303

Last Date Modified: 07/04/2016 07:22 AM


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